Proteins regulating gene transcription have been identified, characterized, and classified based on common structural motifs. One motif identified in a growing family of transcription factors is the basic helix-loop-helix (bHLH) domain. Proteins manifesting the BHLH domain participate in the regulation of cell specification and differentiation. For example proteins from the Drosophila achaete-scute complex, regulate neuronal development. A CDNA clone encoding a novel member of the BHLH protein superfamily homologous to these proteins has been isolated from a catfish (Ictalurus punctatus) olfactory epithelium CDNA library. This BHLH protein, named CASH (catfish achaete-acute homolog) is particularly interesting as olfactory epithelium contains neuronal precursors capable of continuous division and differentiation to form olfactory neurons. In light of the role that BHLH transcription factors play in the regulation of cell specification and differentiation, this proposal will study and characterize this BHLH protein and the role in plays in regulating gene expression. To achieve this we plan to; -determine the tissue and cell distribution of the CASH MRNA; express the CASH BHLH protein for antiserum production for immunocytochemical localization and functional studies; identify the DNA sequence motif to which the CASH BHLH protein binds; characterize homo- and heteromeric protein-protein interactions of the CASH protein; evaluate the role of post-translational modifications on the activities of this proteins; identify and characterize the genes that the CASH protein interacts with and evaluate how they are regulated; determine if there are other related BHLH proteins in olfactory mucosa of teleosts and other vertebrates. This will expand knowledge of the BHLH family of transcription factors and advance our understanding of the molecular basis by which these proteins regulate gene transcription. Detailed knowledge of BHLH proteins and the normal mechanisms by which they regulate gene transcription is critical in understanding how disturbances in gene transcription result in metabolic and degenerative diseases associated with aging, oncogenesis, and in response to trauma. This research, coupled with coursework in neuroscience and molecular biology, will upgrade the applicant's skills and serve as an essential bridge for her process and development as an independent investigator so that she may eventually obtain an academic position to pursue independent research studying gene regulation in the nervous system.